1. Field of the Invention
The invention relates to apparatus for applying marks to the surface of a product, especially the cylindrical surface of a coil of material such as rolled steel.
2. Description of the Prior Art
It is known for marks to be applied to a coil of rolled steel by means of a stencil and spray gun. This process is labour-intensive and, with a hot product, such as a coil of hot-rolled steel which has a temperature of e.g. 350.degree. C., difficult and unpleasant for the marker. Another less difficult known method for marking products, is for alpha-numeric symbols to be applied to a product in the form of small dots sprayed by a matrix by programmed spray guns. The present invention is especially applicable to the design of apparatus for applying marks using these programmed spray guns or similar marking apparatus, but is not restricted to this application.
DAS No. 27 16 626 (Hoesch) discloses a spray gun for marking metal coils which is mounted on a carriage which moves along a segmental horizontal track. This track itself is movable vertically. By coordination of these movements, symbols can be written on the coil by the spray gun. A number of motors is required to control this apparatus, and its control is complex and delicate.